The present invention relates to computer controlled pattern cutting machines and pertains particularly to a system including means for adapting graphics plotters to sheet cutting machines.
Many sign makers in recent years have gone to paste on vinyl lettering in place of painted letters of the past. The development of thin plastic films, such as vinyl films has enabled this development to take place. Most sign lettering today is formed from thin sheets of vinyl having a strong adhesive on the back surface thereof for mounting on sign boards, panels and the like. A suitable film for this purpose is available and has been available from the 3M Company under the Trademark "Scotchcal" film. This material comes in the form of a thin sheeting of vinyl on the order of approximately three thousandths of an inch thick mounted on a wax paper backing or carrier.
Up until approximately four to five years ago, lettering was cut from such sheets by means of patterns or the like or by hand. Approximately four to five years ago, a letter cutting machine similar to a computer controlled plotter was developed by Gerber Scientific Products, Inc. for the purpose of cutting forms and lettering from this sheet material. The Gerber Scientific Products, Inc. machines are available in two models identified as the GSP Signmaker IV or Graphix 4. These machines have a sheet feed or roll feed device in the form of a pin sprocket or tractor feed as they are sometimes termed with a movable carriage having a knife rotably mounted thereon for cutting the desired patterns.
The mechanism of the presently available device utilizes a knife and carriage arrangement, as illustrated in FIG. 1, wherein a knife blade 10 is mounted on the end of a rotatable shaft 12, which is mounted in a shaft such that the shaft will rotate about an axis corresponding to the point of the knife 10. The shaft 12 is rotated about this axis by means of a sprocket and drive arrangement comprising a sprocket 14 driven by a belt 16 from a motor 18, which is in the form of a stepper motor or a synchronous motor. The motor is programmed along with the carriage and drive such that the knife is constantly rotated to follow curves in the graphics cutting.
A sheet of material such as a Vinyl sheet 20 on a wax paper backing 22, such as that of the 3M product, is fed past the knife by means of a sprocket drive as previously pointed out. The motor 18 is constantly driven to rotate the knife such that the knife points in the direction of the cut in forming the curvatures of the graphics, as shown in FIG. 2. The knife cuts or severs the Vinyl sheeting 20 without extending throught he wax paper backing 22. The cuts are made by a combination of movement of the knife and the sheeting.
Such machines, while satisfactory for many applications, have a number of drawbacks. One of the major drawbacks is the complexity of computer software necessary to maintain the proper control of the knife blade to assure its proper orientation following the curves of the necessary pattern. Other drawbacks include the problem with maintaining the proper orientation by means of the knife rotating drive mechanism. Other drawbacks include the complexity and expense of the device.
I have been in the sign business for many years and have used these machines since their introduction, approximately four to five years ago. In view of the problems with such machines, I have endeavored for the past four years to find or develop an alternative cutting mechanism for replacing such machines. One approach has been to attempt to find some means for adapting the conventional computer controlled graphics plotter to the cutting process. These graphics plotters are available which take the output from a microprocessor or suitable computer and convert it to graphic illustration on sheets fed through the plotter. The plotters employ one or more ink pens, typically felt tip pens, which under the direction and control of the microprocessor follow the desired patterns and form the patterns in ink on sheets of paper on the plotter. Over four years of efforts to find some means or develop some means for employing standard plotters for cutting have until just recently been unsuccessful.
Recently, I conceived and developed the subject of the present invention which is capable of converting the standard ink pen plotters to a computer controlled sheet cutter.